A common, commercially available coupling arrangement between a Kelly bar and a stud or stub shaft of an earth drill drive is illustrated and described in Fehrmann and Rassieur U.S. Pat. No. 3,309,898. A flexible coupling is slidably mounted on the Kelly bar, and is gravity biased toward its free end. It is held out of the way of a drive shaft or stud by means of a pin inserted in a hole in the Kelly bar, and when the Kelly bar and stud are aligned, the pin is pulled and the flexible coupling permitted to engage the stud. In order to disconnect the stud and Kelly bar, the flexible connector is raised manually, and the pin replaced. Especially with large drill rigs, the flexible connector, which is generally made up of heavy steel hubs connected with a heavy chain, is massive and difficult to handle manually. Furthermore, with any size drill rig, there is always the danger that the pin will fall out or not be put in properly, and the coupling will slide off the Kelly bar and into the hole being drilled.
One of the objects of this invention is to provide a Kelly bar coupling arrangement that requires no manual handling of the coupler.
Another object of this invention is to provide such a coupler that can not inadvertently be dropped from the rig.
Yet another object is to provide a coupling system in which uncoupling of the Kelly bar and drive stud is ensured before the mast that carries the Kelly bar can be folded.
Other objects of this invention will be apparent to those skilled in the art in light of the following description and accompanying drawings.